Various types of processors have been developed to support various electronic devices such as smartphones, tablet personal computers, portable multimedia players, personal digital assistants, and laptop personal computers.
In recent years, techniques to reduce power consumed by processors have been developed as part of efforts to reduce power consumed by electronic devices.
In general, reducing power consumed by a processor may be achieved by changing the operating frequency of the processor or by suspending or restricting the usage of the processor.
Dynamic Voltage and Frequency Scaling (DVFS) is a representative technique for changing the operating frequency of a processor. When the workload is high, the operating frequency of the processor is increased; and when the workload is low, the operating frequency of the processor is decreased to reduce power consumption.
Hot plugging is a representative technique for suspending or restricting the usage of a processor. When the workload is low, a core may be transitioned to an offline state (hot-plugged off), reducing the number of available cores. When the workload is high, a core may be transitioned to an online state (hot-plugged in), increasing the number of available cores.
Transitioning a core to an offline state may entail process cleanup, interrupt masking, and timer event cleanup, thereby resulting in a time delay.
The technique for suspending or restricting the usage of a processor, which requires a relatively long delay to transition a core to an offline state, is less frequently used than the technique for changing the operating frequency of a processor.